Network nodes forward data. Network nodes may take form in one or more routers, one or more bridges, one or more switches, one or more servers, or any other suitable communications processing device. The data is commonly formatted as packets and forwarded using forwarding tables. A packet is a formatted unit of data that typically contains control information and payload data. Control information may include: information that identifies sources and destinations, such as addresses, error detection codes like checksums, sequencing information, etc. Control information is typically found in packet headers and trailers. Payload data is typically located between the packet headers and trailers.
Forwarding packets involves various processes that, while simple in concept, can be complex. The processes involved in forwarding packets vary, depending on the type of forwarding method used. Three types of forwarding methods are: unicast; broadcast; and multicast. Each of the three forwarding methods involves its own set of configuration and control processes. Unicast is a method of point-to-point communication most often used when a particular node (known as a source) wishes to send data to another particular node (known as a receiver) and is not concerned with sending the data to multiple receivers. Broadcast is method used when a source wishes to send data to all receivers in a domain, and multicast allows a source to send data to a group of receivers in a domain while preventing the data from being sent to other receivers in the domain.
Multicast is the preferred method of data forwarding for many networks. One reason for this is that multicast is a bandwidth-conserving technology that reduces traffic by simultaneously delivering data to multiple receivers. However, in traditional multicast systems, a relatively large amount of control plane information is used. Setting up and maintaining this control information has a tendency to become complex and costly in terms of computing resources, and can become a major limiting factor in overall network performance.